The present invention relates to cutting torches and, more particularly, to cutting torches with flashback arrestors.
Oxy-fuel cutting torches discharge fuel gas and oxygen from a nozzle for cutting purposes. A typical torch includes a control body for being connected to separate fuel gas and oxygen supplies, tubes for supplying the oxygen and fuel gas from the control body to a head, and a cutting tip mounted to the head. The cutting tip receives the fuel gas and oxygen from the head and discharges these gases from its nozzle. More specifically, the head includes an interior surface extending around and defining a head cavity, an oxygen port that is open to the head cavity for supplying oxygen to the head cavity, and a fuel gas port that is open to the head cavity for supplying fuel gas to the head cavity. The cutting tip includes multiple passageways for directing the gases from the head to the nozzle.
Conventional torches first generate a preheat flame with gases discharged from the nozzle, and the preheat flame is used to heat a metal workpiece. After the preheat flame has heated the workpiece sufficiently, a high velocity cutting oxygen stream is activated and delivered through the nozzle. The high velocity cutting oxygen stream physically removes molten material of the workpiece by oxidation, to cut the workpiece. Typically, a number of valves and related components are provided upstream of the nozzle, such as in the control body, to control the operations of the cutting torch.
Flashback is a reaction caused in cutting torches by the reverse flow and ignition of the explosive mixture of gases used in the operation of the torch. Flashback typically originates at the nozzle of the torch and is often caused by an obstruction at this point, operator error, improper gas pressure and/or defective equipment. Due to the rapid and explosive nature of flashback, it poses a major safety hazard to the operator of the gas torch and can damage the gas torch and associated equipment. Accordingly, and as disclosed in U.S. Pat. Nos. 5,407,348 and 5,470,227, it is common for flashback arrestors constructed of sintered material to be used at the entry point of the gases into the torch. Whereas this stops the flashback from traveling upstream from the torch into the gas hoses, regulators and cylinders that supply the gas to the torch, it disadvantageously does not eliminate the effects of flashback within the torch itself, which means that the torch can be damaged or the operator can be injured by flashback within the torch.
It is also known to install packing material into the head of a torch or in a tube that is immediately upstream from the head for arresting flashback, as respectively disclosed in U.S. Pat. Nos. 1,176,017 and 1,290,422. It is common for this packing material to become damaged, such as by becoming clogged with carbon deposits resulting from flashback. As a result, the packing material must be periodically replaced. Disadvantageously, the removal and replacement of packing material in cutting torches is labor intensive. Additionally, and of significant safety importance, if the packing material is not properly packed it may not perform its intended function, which can result in damage to the torch or injury to its operator.
It is also known for the few gas-carrying passageways that are machined into cutting tips and cutting tip adapters to be shaped so that they have abrupt directional changes which are intended to restrict flashback, as is disclosed in U.S. Pat. Nos. 1,439,861; 3,746,500; 4,431,167 and 5,688,469. However, because there are constraints on the size of some cutting tips, it is common for the number of directional changes that can be efficiently provided by machining passages to be very limited. This limitation can in at least some situations disadvantageously limit the effectiveness of these types of adapters and cutting tips with respect to restricting flashback.
Accordingly, there is a need in the art for a flashback arrestor proximate the head of a cutting torch for restricting flashback into head, and which can be readily used and replaced in a manner that is likely to ensure satisfactory functionality of the flashback arrestor.
In accordance with one aspect of the present invention, flashback protection is provided proximate the head of a cutting torch by a fitting, which is preferably in the form of an adapter or a cutting tip for mounting to the head. In accordance with this aspect, the fitting includes a body and porous structure that is carried by the body and is a distinct component from the body. The porous structure has a multiplicity of convolute passageways extending therethrough for restricting flashback, preferably by safely extinguishing any flashback proximate its source. Further in accordance with this aspect, the fitting can be readily used and replaced in a manner that is likely to ensure optimum functionality. Preferably for each fitting the porous structure is carried by the body in a manner that promotes the disposal of the used fitting rather than just the replacement of the porous structure of the fitting, which promotes safe operation of cutting torches by inhibiting end users from improperly installing the porous structure. Alternatively, the porous structure can be readily removable from the fitting and is replaceable.
In accordance with one aspect of one embodiment of the present invention, an end of the body of the fitting is inserted into the cavity of a head when mounting the fitting to the head, the end of the body is withdrawn from the cavity when unmounting the fitting from the head, the body defines at least one oxygen passageway that is in communication with the oxygen port of the head for receiving oxygen while the body is mounted to the head, the fitting defines at least one and preferably a plurality of fuel gas passageways that are in communication with the fuel port of the head for receiving fuel gas while the body is mounted to the head, and the porous structure is associated with the body so that the porous structure restricts flashback from entering the fuel port of the head while the body is mounted to the head. In addition, the porous structure is carried by the body so that it moves with the body when the body is moved from being completely separate from the head to being mounted to the head, and when the body is being moved from being mounted to the head to being completely separate from the head. As a result, the fitting can be easily initially installed and replaced with minimal risk of the porous structure being incorrectly installed and thereby failing to perform its intended function. Preferably the porous structure is positioned in the fuel passageways to restrict flashback through the fuel passageways.
In accordance with another aspect, a first part of the body is mounted to a second part of the body so that surfaces of these parts together define a chamber that contains the porous structure. This advantageously seeks to render the fitting tamper resistant and thereby enhance the disposable aspect of the fitting. That is, and in addition to the fitting being constructed so as to minimize the risk of the porous structure being incorrectly installed, in accordance with the present aspect a user will preferably be unaware of the possibility of disassembling the fitting to replace the porous structure should it become clogged, which will advantageously minimize the possibility of a user incorrectly installing a replacement porous structure within the fitting. Alternatively, the porous structure can be readily removable from the fitting and is replaceable.
In accordance with another aspect, the outer part of the body includes upstream fuel passageways, and the inner part of the body includes downstream fuel passageways. Further in accordance with this aspect, the inner part of the body includes a bore, the outer part of the body includes the oxygen passageway, and the oxygen passageway extends through the bore. Preferably the fuel gas passageways are positioned around and radially distant from the oxygen passageway.
In accordance with another aspect, the fitting is a cutting tip. In contrast and in accordance with another aspect of the present invention, the fitting is an adapter for having a cutting tip mounted thereto. In accordance with this aspect, there are multiple annular chambers that extend around and are isolated from the oxygen passageway, and that are open to the fuel gas passageways.
In accordance with one aspect of another embodiment of the present invention, the fitting is mounted to the head by engaging threads of the body to threads of head and rotating the body relative to the head through a plurality of revolutions in a first direction. Accordingly, the body can be unmounted from the head by causing relative rotation between the head and the body through a plurality of revolutions in a second direction which is opposite from the first direction. The porous structure is fitted to the body to restrict flashback from entering the fuel port of the head. As a result, the fitting can be easily initially installed and replaced with minimal risk of the porous structure being incorrectly installed and thereby failing to perform its intended function, since the porous structure is fitted to the body for installation and removal therewith. Alternatively, the fitting can be mounted to the head by means other than threads.
In accordance with another aspect, the fitting is an adapter and a cutting tip is mounted to the head via the adapter. Preferably the porous structure is annular and thereby defines a bore through which the cutting tip extends.
In accordance with another aspect, the fitting includes a port having an axis that extends radially with respect to the axis of the body. Preferably the body includes a channel that is adjacent and at least partially encircles the porous structure and is for passing fuel between the port and convolute passageways of the porous structure.
In accordance with another aspect, the porous structure is press-fit to the body, and in accordance with this same or another aspect, the porous structure is secured to the body by at least one fastening device, such as a pin-like shaft, that penetrates the porous structure and the body. This advantageously seeks to render the fitting tamper resistant and disposable. That is, the porous structure is preferably securely mounted to the body such that it will be difficult or at least inconvenient for a user to disassemble the fitting to replace the porous structure should it become clogged, which will advantageously minimize the possibility of a user incorrectly installing a replacement porous structure in the fitting. Alternatively, the porous structure can be readily removable from the fitting and is replaceable.
It is accordingly an aspect of the present invention to promote safe use of a cutting torch by suppressing flashback proximate its source through the use of a fitting that is substantially fool-proof, such as, for example, by being disposable.